Vehicle engine fuel systems typically comprise a fuel tank, a fuel feed line running from the tank to the engine, a pump for transferring fuel from the tank through the fuel feed line to the engine, and a return line for returning unused fuel from the engine to the tank. This is a one-way system, and it is typically not desirable to have fuel flowing from the tank through the fuel return line.
In an accident or vehicle roll-over situation such reverse flow can be extremely dangerous, particularly if the return line were ruptured, due to the threat of igniting or fueling a fire with the entire content of the fuel tank as it escaped from the tank through the return line. Reverse fuel flow is also undesirable in a vehicle service situation in which a mechanic might disconnect the return line at the engine to perform repairs. When disconnected, the end of the return line nearest the engine might be lower than the tank and the entire tank might drain through the return line onto the floor of the service facility or into a water drain.
A known method for safeguarding against reverse flow of the fuel from the fuel tank through the return line has been to place a one-way check valve in the return line, typically near or actually in the fuel tank. Such a valve opens to allow fuel to flow from the return line to the tank, but closes to prevent fuel from flowing from the tank back through the return line.
Although check valves are well-known in the art, the prior art valves currently in use to prevent reverse fuel flow from the fuel tank to the return line are often complicated and expensive to manufacture, unreliable, or slow in operation.